/*

 * jdct.h

 *

 * Copyright (C) 1994, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This include file contains common declarations for the forward and

 * inverse DCT modules.  These declarations are private to the DCT managers

 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.

 * The individual DCT algorithms are kept in separate files to ease 

 * machine-dependent tuning (e.g., assembly coding).

 */





/*

 * A forward DCT routine is given a pointer to a work area of type DCTELEM[];

 * the DCT is to be performed in-place in that buffer.  Type DCTELEM is int

 * for 8-bit samples, INT32 for 12-bit samples.  (NOTE: Floating-point DCT

 * implementations use an array of type FAST_FLOAT, instead.)

 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).

 * The DCT outputs are returned scaled up by a factor of 8; they therefore

 * have a range of +-8K for 8-bit data, +-128K for 12-bit data.  This

 * convention improves accuracy in integer implementations and saves some

 * work in floating-point ones.

 * Quantization of the output coefficients is done by jcdctmgr.c.

 */



#if BITS_IN_JSAMPLE == 8

typedef int DCTELEM;		/* 16 or 32 bits is fine */

#else

typedef INT32 DCTELEM;		/* must have 32 bits */

#endif



typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));

typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));





/*

 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer

 * to an output sample array.  The routine must dequantize the input data as

 * well as perform the IDCT; for dequantization, it uses the multiplier table

 * pointed to by compptr->dct_table.  The output data is to be placed into the

 * sample array starting at a specified column.  (Any row offset needed will

 * be applied to the array pointer before it is passed to the IDCT code.)

 * Note that the number of samples emitted by the IDCT routine is

 * DCT_scaled_size * DCT_scaled_size.

 */



/* typedef inverse_DCT_method_ptr is declared in jpegint.h */



/*

 * Each IDCT routine has its own ideas about the best dct_table element type.

 */



typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */

#if BITS_IN_JSAMPLE == 8

typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */

#define IFAST_SCALE_BITS  2	/* fractional bits in scale factors */

#else

typedef INT32 IFAST_MULT_TYPE;	/* need 32 bits for scaled quantizers */

#define IFAST_SCALE_BITS  13	/* fractional bits in scale factors */

#endif

typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */





/*

 * Each IDCT routine is responsible for range-limiting its results and

 * converting them to unsigned form (0..MAXJSAMPLE).  The raw outputs could

 * be quite far out of range if the input data is corrupt, so a bulletproof

 * range-limiting step is required.  We use a mask-and-table-lookup method

 * to do the combined operations quickly.  See the comments with

 * prepare_range_limit_table (in jdmaster.c) for more info.

 */



#define IDCT_range_limit(cinfo)  ((cinfo)->sample_range_limit + CENTERJSAMPLE)



#define RANGE_MASK  (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */





/* Short forms of external names for systems with brain-damaged linkers. */



#ifdef NEED_SHORT_EXTERNAL_NAMES

#define jpeg_fdct_islow		jFDislow

#define jpeg_fdct_ifast		jFDifast

#define jpeg_fdct_float		jFDfloat

#define jpeg_idct_islow		jRDislow

#define jpeg_idct_ifast		jRDifast

#define jpeg_idct_float		jRDfloat

#define jpeg_idct_4x4		jRD4x4

#define jpeg_idct_2x2		jRD2x2

#define jpeg_idct_1x1		jRD1x1

#endif /* NEED_SHORT_EXTERNAL_NAMES */



/* Extern declarations for the forward and inverse DCT routines. */



EXTERN void jpeg_fdct_islow JPP((DCTELEM * data));

EXTERN void jpeg_fdct_ifast JPP((DCTELEM * data));

EXTERN void jpeg_fdct_float JPP((FAST_FLOAT * data));



EXTERN void jpeg_idct_islow

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));

EXTERN void jpeg_idct_ifast

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));

EXTERN void jpeg_idct_float

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));

EXTERN void jpeg_idct_4x4

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));

EXTERN void jpeg_idct_2x2

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));

EXTERN void jpeg_idct_1x1

    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,

	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));





/*

 * Macros for handling fixed-point arithmetic; these are used by many

 * but not all of the DCT/IDCT modules.

 *

 * All values are expected to be of type INT32.

 * Fractional constants are scaled left by CONST_BITS bits.

 * CONST_BITS is defined within each module using these macros,

 * and may differ from one module to the next.

 */



#define ONE	((INT32) 1)

#define CONST_SCALE (ONE << CONST_BITS)



/* Convert a positive real constant to an integer scaled by CONST_SCALE.

 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,

 * thus causing a lot of useless floating-point operations at run time.

 */



#define FIX(x)	((INT32) ((x) * CONST_SCALE + 0.5))



/* Descale and correctly round an INT32 value that's scaled by N bits.

 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding

 * the fudge factor is correct for either sign of X.

 */



#define DESCALE(x,n)  RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)



/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.

 * This macro is used only when the two inputs will actually be no more than

 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a

 * full 32x32 multiply.  This provides a useful speedup on many machines.

 * Unfortunately there is no way to specify a 16x16->32 multiply portably

 * in C, but some C compilers will do the right thing if you provide the

 * correct combination of casts.

 */



#ifdef SHORTxSHORT_32		/* may work if 'int' is 32 bits */

#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT16) (const)))

#endif

#ifdef SHORTxLCONST_32		/* known to work with Microsoft C 6.0 */

#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT32) (const)))

#endif



#ifndef MULTIPLY16C16		/* default definition */

#define MULTIPLY16C16(var,const)  ((var) * (const))

#endif



/* Same except both inputs are variables. */



#ifdef SHORTxSHORT_32		/* may work if 'int' is 32 bits */

#define MULTIPLY16V16(var1,var2)  (((INT16) (var1)) * ((INT16) (var2)))

#endif



#ifndef MULTIPLY16V16		/* default definition */

#define MULTIPLY16V16(var1,var2)  ((var1) * (var2))

#endif

